The communication system that is a successor to the Wideband Code Division Multiple Access (WCDMA) system and High Speed Uplink Packet Access (HSUPA) system i.e. the Long Term Evolution (LTE) system has been studied by 3GPP that is the standardization group of WCDMA, and the specification development work has proceeded. As a radio access scheme in LTE, Orthogonal Frequency Division Multiplexing Access (OFDMA) is defined in downlink, while Single-Carrier Frequency Division Multiple Access (SC-FDMA) is defined in uplink (for example, see Non-patent literature 1 for the details).
The OFDMA system is a multicarrier transmission system for dividing a frequency band into a plurality of narrow frequency bands (subcarriers), and assigning data to each frequency band to perform transmission. High-speed transmission is actualized by densely arranging subcarriers in the frequency domain to be orthogonal to one another, and it is expected to enhance spectral efficiency.
The SC-FDMA system is a single-carrier transmission system for dividing the frequency band for each terminal, and performing transmission using different frequency bands among a plurality of terminal. The system is capable of reducing interference among the terminals with ease and efficiency, and further decreasing variations in the transmission power, and therefore, is preferable from the viewpoints of power consumption in the terminal, increases in coverage and the like.
In LTE, in both of downlink and uplink, one or more resource blocks are assigned to a mobile terminal to perform communications. A base station apparatus determines a mobile terminal, to which it assigns resource blocks, from among a plurality of mobile terminals for each sub-frame (1 ms in LTE) (this process is called scheduling.) In downlink, the base station apparatus transmits a shared channel to the mobile terminal selected in scheduling in one or more resource blocks. In uplink, the selected mobile terminal transmits a shared channel to the base station apparatus in one or more resource block. In addition, the shared channel is the PUSCH in uplink, while being the PDSCH in downlink.
Meanwhile, in LTE, random access is used for initial connection, etc. The channel for random access is referred to as the Physical Random Access channel (PRACH). Further, the mobile terminal transmits a random access preamble on the Physical Random Access Channel. The details of the Physical Random Access Channel and the random access preamble are defined, for example, in Non-patent literature 1.
In addition, in cellular telephones, radio astronomy, satellite communications, aeronautical/marine radar, earth resources satellite and wireless LAN, used frequency bands are divided to prevent mutual interference. Further, for example, a plurality of systems exits in the frequency band assigned to the system of cellular telephone, and the frequency band of each system is divided.
In other words, in the systems using radio signals, interference among the systems is prevented by dividing the used frequency bands. However, since a transmitter that radiates radio signals radiates unwanted emissions (hereinafter, referred to as adjacent channel interference) in bands outside the frequency band of the system, even when the frequency bands are divided, a plurality of adjacent systems mutually imposes interference. Accordingly, when the power level of the unwanted emissions is high, the serious adverse effect is given to the adjacent system.
To prevent the adverse effect on the adjacent system by such adjacent channel interference, performance concerning the adjacent channel interference and characteristics on spurious emission is specified in each system. For example, in the LTE system, as the specification on adjacent channel interference, spurious emission and the like in a mobile terminal, 6.6 Output RF spectrum emissions in TS36.101 exists (Non-patent literature 2).
In addition, to suppress the above-mentioned unwanted emissions to outside the system band, the mobile terminal needs to be equipped with a power amplifier with high linearity. Accordingly, in the case of considering the cost and size of the mobile terminal, there are cases that it is difficult to reduce the above-mentioned unwanted emissions, or meet the specification of adjacent channel interference and the specification of spurious emission as described above. In this case, for example, in Non-patent literature 2 as described above, to suppress the cost and size of the mobile terminal, it is specified to reduce the maximum transmission power on some condition. The reduction in the maximum transmission power is referred to as Maximum power reduction (MPR). For example, in LTE, the MPR is defined based on the modulation scheme, system bandwidth and the number of resource blocks (Non-patent literature 2, Table 6.2.3-1). By reducing the maximum transmission power, it is possible to control the cost and size of the mobile terminal to within small values.